> For the complete documentation index, see [llms.txt](https://docs.idlayr.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.idlayr.com/products/risk/sim-swap.md).

# SIM Swap

{% hint style="info" %}
**Backend API** · GA
{% endhint %}

Detect whether the SIM card associated with a mobile phone number has recently changed, by querying the mobile network operator in real time. Used as a pre-transaction risk signal to flag account-takeover risk before high-value actions.

SIM Swap is a backend-to-backend API. No mobile SDK, no device involvement, no cellular-data path. Your backend sends a phone number; IDlayr returns a deterministic SIM-change result.

## What it does

* Queries the MNO's live subscriber record for the supplied phone number.
* Returns a deterministic `no_sim_change` boolean — `true` when the SIM hasn't recently changed, `false` when it has.
* Operates entirely server-to-server. The end user is not involved at any step; the check is invisible to them.
* Sub-second response time on supported networks.

## What it doesn't do

* Doesn't authenticate the person or the device — SIM Swap is a risk signal, not a proof factor. Pair with [Secure SNA](/products/number-verification/secure-sna.md) when device-and-number trust also matters.
* Doesn't distinguish a fraudulent SIM swap from a legitimate one (an upgrade, a replacement). The customer's business logic decides what a positive result means.
* Doesn't return SIM-change history. It tells you whether a change happened within a recent window — the boundary is defined by the MNO and IDlayr's contract.

## Common use cases

* **Harden SMS OTP** — check for a recent SIM swap before delivering an OTP. If positive, route to an alternative verification method.
* **Strengthen Secure SNA** — pair SIM Swap with SNA. Together, they confirm both that the device holds the number and that the SIM hasn't recently changed.
* **Account-login and step-up protection** — flag suspicious recent SIM activity before password resets, device changes, or payment approvals.
* **Onboarding risk assessment** — check whether the number a new user is signing up with is associated with a recent SIM change.
* **Payment and transaction protection** — pre-transaction check in banking, fintech, and e-commerce flows.

## In this section

* [**How it works**](/products/risk/sim-swap/how-it-works.md) — the backend-to-MNO query flow.
* [**Prerequisites**](/products/risk/sim-swap/prerequisites.md) — what you need before integrating.
* [**Integration**](/products/risk/sim-swap/integration.md) — backend-to-backend integration walkthrough.
* [**Testing in sandbox**](/products/risk/sim-swap/testing.md) — sandbox MSISDN patterns for SIM Swap.
* [**Endpoints**](/products/risk/sim-swap/endpoints.md) — REST endpoint summary; full reference in API Reference.
* [**Error codes**](/products/risk/sim-swap/error-codes.md) — HTTP errors and terminal-state codes specific to SIM Swap.


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